my step kid is picking on my bio kids... read update below

update .... i threatened to cancel the sleepover and she stormed outside and then my 6yo went out to draw with her and came inside crying saying she had told her they cant be friends .... im just so fucking done today. today is my tstep daughters 10th birthday. Anyone would think shes just turned 15 the attitude im copping.

I went out and bought her $60 worth of presents (left myself basically flat broke because I wanted to get her the present she really wanted) and she woke up and is sitting there with it not allowing the other kids to go near it making them cry (6 yo, 2yo and 1yo). I get that its her present but its 11am and im wishing i never bought it.

My 6yo has been pinched and told to shut up and go away already, she ripped a pen out of the 2yos hand and nearly ripped her finger off with it, and has been sitting here mocking my 6yo saying "you dont get to play with it too hahaha" so i told her dad and she then denied doing any of it and hes like "its her bday present" ....

Anyway, tonight my fiance goes to work night shift and i have her friend coming for a sleepover and im dreading having to deal with the bitchiness on my own. Not to mention shes put her order in she wants pizza ordered and im now broke and i said no so shes chucked a hissy fit over it... so bloody spoilt she is.

I just know this is the start. Will only get worse now shes getting older. Any advice?***also now because we cant afford pizza her dad is borrowing money off his brother to buy pizza for her for dinner because cheaper alternatives are not an option fml ***